Electronic ignition compensation



Feb. 13,1968 C.M.AULT 3,368,540

ELECTRONIC IGNITION COMPENSATION Filed March 4, 1966 DISTRIBUTOR ANDSPARK PLUGS STARTING SOLENOID IGNITION COIL CLIFFORD M. AULT BY 7 Z/ATTORNEY INVENTOR United States Patent 3,368,540 ELECTRONIC IGNITIONCOMPENSATION Clilford M. Ault, 5341 Glencairn Lane, Indianapolis, Ind.46226 Filed Mar. 4, 1966, Ser. No. 531,943 3 Claims. (Cl. 123179) Thisinvention relates generally to an ignition system for internalcombustion engines, and more particularly to an ignition systemincluding means operable during the starting of an engine for applyingupon the high tension ignition circuitry a temperature-compensatedauxiliary power input.

In the prior art, ignition systems for internal combustion engines havebeen proposed that includes a ballast resistor connected in series withthe ignition coil primary winding to maintain a safe continuous primarycurrent. This resistor, which is shunted during the starting periodonly, is generally incapable of sensing changes in starting load thatoccur with variations in ambient temperature. Thus, the starting load atlow ambient temperature may reduce the available high tension voltagebelow the point at which the normally combustible mixture may beignited. More particularly, since the flash point of the fuel mixtureincreases and battery voltage decreases as ambient temperaturedecreases, the starting of internal cornbustion engines is rendereddifficult under cold weather conditions.

The present invention Was developed to provide an improvedtemperature-responsive voltage compensator for providing additionalpower to the high tension ignition circuitry of an internal combustionengine during the starting period. The compensating circuit is designedto provide only that energy necessary to maintain the high tensionvoltage at an optimum value.

The primary object of the present invention is to provide an improvedignition system including means operable during the engine startingperiod for introducing a temperature-compensated auxiliary current intothe ignition coil circuit. The invention is characterized in thatvoltage compensation is generated during the starting period as afunction of ambient temperature. According to the preferred embodimentof the invention, use is made of a temperature-responsive resistorhaving a positive temperature coeflicient for controlling the magnitudeof the voltage induced in a secondary winding connected in series withthe ignition coil and the supply battery. The resistor is preferablyconnected in series with free-running oscillator means which include aprimary winding inductively coupled to the aforementioned secondarywinding. The improved compensation means may be installed either as apermanent part of the ignition system or is an auxiliary system that maybe by-passed to permit conventional engine operation during warmweather.

A more specific object of the invention is to provide an ignition systemof the type described above including transformer means having primaryand secondary windings, said primary winding comprising an inductivecomponent of oscillator means that are energized by the battery throughthe START contact of an ignition switch. According to the preferredembodiment of the invention, a temperature-responsive resistor isconnected in series with the battery and the oscillator. The secondarywinding is connected to the ignition coil and is energized, duringengine starting, by induction as a function of the operation of thetemperature compensated oscillator means. During the engine runningperiod, the oscillator means are deactivated; the secondary winding andrectifier form a low impedance path to the normal current flow and otteran insignificant voltage drop which can be ignored.

The present invention offers the advantage that the output of thecompensating voltage generator means increases as the ambienttemperature decreases, as effected by the use of a biasing resistorhaving a positive temperature coefficient. Moreover, as a consequence ofthe invention, the starting efliciency achieved by the additive energycompensation is relatively high and the demand on the prime power sourceis insignificant.

Other objects and advantages of the invention will become apparent froma study of the accompanying drawing, the single figure of which is anelectrical schematic diagram of the ignition system of the presentinvention.

Referring to the drawing, the ignition system includes a battery 2having a grounded negative terminal, and a positive terminal connectedto the movable contact 4 oi a three-position ignition switch 6. Theswitch contact 4, which carries a bridging head portion 4a, is movablebetween positions in electrical engagement with the stationary OFF, ON,and START contacts 8, 10 and 12, respectively. The configuration of thebridging portion 4a is such that it bridges both contacts 10 and 12 whencontact 4 is pivoted to the START position. The ON contact 10 isconnected with one terminal of ignition coil 14 via winding 16, diode18, and a conventional ballast resistor 19. Connected across the seriesbranch including winding 16 and diode 18 is a filter capacitor 20.

Winding 16 comprises the secondary winding of a transformer 28 having aprimary winding 30 which forms an inductive component of conventionaloscillator means 32. More particularly, the oscillator means 32 includesa pair of transistors 34, 36 the emitters of which are connected withthe START contact 12 via conductor 40. The collector electrodes of thetransistors are connected with opposite ends of the primary Winding 30,respectively. The base electrodes of transistors 34, 36 are connectedwith the collectors of transistors 36, 34 via resistancecapacitancebiasing networks 42, 44, respectively. The center tap 46 of primarywinding 30 is connected with the grounded negative terminal of battery 2by conductor 48 which contains in series with the oscillator 32 anambient temperature-responsive resistor 50. In the illustrate-dembodiment, the resistor 50 has a positive temperature coeflicient. Theconventional starting solenoid 52 is connected between START contact 12and ground.

Operation When movable ignition switch contact 4 is pivoted to the STARTposition, contacts 10 and 12 are bridged by bridging portion 4a, andstarting solenoid 52 is energized to effect driving of the crank shaftof the internal combustion engine by starter motor means, not shown.Positive battery voltage is applied to the emitter electrodes oftransistors 34, 36 via conductor 40, and since the center tap 46 ofwinding 30 is connected with ground via temperature-responsive resistor50, the oscillator 32 is activated and commences oscillation at afrequency dependent upon the time constants of resistance-capacitancebranches 42, 44, and the characteristics of the transformer windings andcore material. Owing to transformer action, an alternating currentvoltage is induced in secondary winding 16 that is rectified by diode18, filtered by capacitor 20, and is added to the normal direct currentthat is supplied from the battery 2 to one terminal of coil 14 viaswitch 6, contact 10, coil 16, diode 18 and ballast resistor 19. Currentis then supplied to the spark plugs via the distributor to effectignition of the fuel and starting of the internal combustion engine.

In accordance with the present invention, the additive (i.e., auxiliary)voltage applied to the high tension circuit is controlled as a functionof ambient temperature to compensate for the variations in batteryvoltage and in the ignition flash point of the fuel that result fromvariations in temperature. To this end, the resistor 50 has such apositive temperature coefiicient that as the ambient temperatureincreases, the resistance of resistor 50 increases to reduce the currentflowing from the positive terminal, through the oscillator 32 andresistor 50, and back to the battery negative terminal and ground. Sincethe current flowing through (i.e., the voltage applied across) theoscillator is reduced, the voltage induced in secondary winding 16 andthe current supplied to ignition coil 14 is reduced correspondingly.Since the flash point of the fuel decreases with the increase intemperature, the spark plug cylinders are efficiently fired through theuse of only that energy necessary to maintain the high tension systemlevel at an optimum value.

In the event that ambient temperature decreases, the battery potentialfalls and the flash point of the fuel increases. Since the resistance ofresistor 50 decreases, the potential applied across oscillator 32increases, whereby the voltage induced in secondary winding 16 and thecorresponding level of the current supplied to ignition coil 14 areincreased.

When the engine has been started, the ignition switch contact 4 ispivoted to the ON position (in which bridging portion 4a merely engagesthe contact and battery current continues to be supplied to the ignitioncoil 14 via secondary winding 16 and diode 18. Since the opencircuitedoscillator 32 is de-activated, no auxiliary voltage is induced in thesecondary winding 16.

While the invention has been described in connection with an ignitionsystem including an oscillator of the solid state, free-running type, itis apparent that energy generation might be accomplished by vibratingreeds, silicon controlled rectifier switches, mechanical breakers, andassociated voltage transforming and rectifying devices. It will also beapparent to those skilled in the art that other changes andmodifications may be made in the apparatus described without deviatingfrom the invention set forth in the following claims.

What is claimed is:

1. In an internal combustion engine ignition system, the combinationwhich comprises,

a battery including a positive terminal and a grounded negativeterminal;

an ignition coil having an output end adapted for connection with thespark plug of the engine, and an input end;

ignition switch means including START and RUN positions;

first means operable when said switch means is in the RUN position forconnecting said positive battery terminal with the input end of saidignition coil; second means operable when said switch means is in theSTART position for supplying a starting current to the input end of saidignition coil; and

temperature-responsive means operable when said switch means is in theSTART position for controlling as a function of ambient temperature themagnitude of the starting current supplied to said ignition coil,

said first means including a secondary winding and a rectifier meansconnected in series between said ignition switch means and the input endof said ignition coil and a filter capacitor connected in parallel withsaid secondary winding and said rectifier,

said second means including a primary winding inductively coupled withsaid secondary winding and circuit means including an oscillator means,

said temperature responsive means including a temperature-responsiveresistor, wherein said oscillator means comprises a pair of electronicdevices each having a pair of power circuit electrodes and a controlelectrode, the ends of said primary winding being connected withcorresponding first power circuit electrodes of said electronic devices,respectively, the other power circuit electrodes of said devices beingconnected with the START contact of said ignition switch, saidtemperature-responsive resistor being connected at one end with thecenter of said primary winding and at the other end with said groundednegative terminal, and a pair of resistancecapacitance biasing networkseach connecting the control electrode of one device with the first:power circuit electrode of the other device, respectively.

2. Apparatus as defined in claim 1 wherein said temperature-responsiveresistor has a positive temperature coefiicient.

3. Apparatus as defined in claim 1, and further wherein said switchmeans includes a conductive bridging portion carried by said movablecontact for electrically connecting said START and RUN contacts onlywhen said movable contact is in the START position, whereby rectifiedtemperature-compensated auxiliary power is added to the normal batterysupply during the engine starting period.

References Cited UNITED STATES PATENTS 2,846,992 8/1958 Short et al.2,980,093 4/1961 Short. 3,026,451 3/1962 Richardson. 3,152,281 10/1964Robbins. 3,170,451 2/1965 Fortier.

LAURENCE M. GOODRIDGE, Primary Examiner.

1. IN AN INTERNAL COMBUSTION ENGINE IGNITION SYSTEM, THE COMBINATIONWHICH COMPRISES, A BATTERY INCLUDING A POSITIVE TERMINAL AND A GROUNDEDNEGATIVE TERMINAL; AN IGNITION COIL HAVING AN OUTPUT END ADAPTED FORCONNECTION WITH THE SPARK PLUG OF THE ENGINE, AND AN INPUT END; IGNITIONSWITCH MEANS INCLUDING START AND RUN POSITIONS; FIRST MEANS OPERABLEWHEN SAID SWITCH MEANS IS IN THE RUN POSITION FOR CONNECTING SAIDPOSITIVE BATTERY TERMINAL WITH THE INPUT END OF SAID IGNITION COIL;SECOND MEANS OPERABLE WHEN SAID SWITCH MEANS IS IN THE START POSITIONFOR SUPPLYING A STARTING CURRENT TO THE INPUT END OF SAID IGNITION COIL;AND TEMPERATURE-RESPONSIVE MEANS OPERABLE WHEN SAID SWITCH MEANS IS INTHE START POSITION FOR CONTROLLING AS A FUNCTION OF AMBIENT TEMPERATURETHE MAGNITUDE OF THE STARTING CURRENT SUPPLIED TO SAID IGNITION COIL,SAID FIRST MEANS INCLUDING A SECONDARY WINDING AND A RECTIFIER MEANSCONNECTED IN SERIES BETWEEN SAID IGNITION SWITCH MEANS AND THE INPUT ENDOF SAID IGNITION COIL AND A FILTER CAPACITOR CONNECTED IN PARALLEL WITHSAID SECONDARY WINDING AND SAID RECTIFIER, SAID SECOND MEANS INCLUDING APRIMARY WINDING INDUCTIVELY COUPLED WITH SAID SECONDARY WINDING ANDCIRCUIT MEANS INCLUDING AN OSCILLATOR MEANS, SAID TEMPERATURE RESPONSIVEMEANS INCLUDING A TEMPERATURE-RESPONSIVE RESISTOR, WHEREIN SAIDOSCILLATOR MEANS COMPRISES A PAIR OF ELECTRONIC DEVICES EACH HAVING APAIR OF POWER CIRCUIT ELECTRODES AND A CONTROL ELECTRODE, THE ENDS OFSAID PRIMARY WINDING BEING CONNECTED WITH CORRESPONDING FIRST POWERCIRCUIT ELECTRODES OF SAID ELECTRONIC DEVICES, RESPECTIVELY, THE OTHERPOWER CIRCUIT ELECTRODES OF SAID DEVICES BEING CONNECTED WITH THE STARTCONTACT OF SAID IGNITION SWITCH, SAID TEMPERATURE-RESPONSIVE RESISTORBEING CONNECTED AT ONE END WITH THE CENTER OF SAID PRIMARY WINDING ANDAT THE OTHER END WITH SAID GROUNDED NEGATIVE TERMINAL, AND A PAIR OFRESISTANCE CAPACITANCE BIASING NETWORKS EACH CONNECTING THE CONTROLELECTRODE OF ONE DEVICE WITH THE FIRST POWER CIRCUIT ELECTRODE OF THEOTHER DEVICE, RESPECTIVELY.